http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57878
wmi at google dot com changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |wmi at google dot com
--- Comment #3 from wmi at google dot com ---
Seems problem is at deciding the priority of assign hardreg for reload pseudos
.i.e the func reload_pseudo_compare_func.
This is the trace of 2nd iteration of reload pseudo assignments in
r.ii.209r.reload:
2nd iter for reload pseudo assignments:
Reload r196 assignment failure
Reload r199 assignment failure
Reload r204 assignment failure
Reload r204 assignment failure
Spill reload r194(hr=1, freq=1426)
Spill reload r195(hr=5, freq=1426)
Spill reload r197(hr=1, freq=1426)
Spill reload r198(hr=5, freq=1426)
Spill reload r202(hr=1, freq=1426)
Spill reload r203(hr=5, freq=1426)
Assigning to 194 (cl=GENERAL_REGS, orig=138, freq=1426, tfirst=190,
tfreq=4991)...
Assign 1 to reload r194 (freq=1426)
Assigning to 197 (cl=GENERAL_REGS, orig=138, freq=1426, tfirst=190,
tfreq=4991)...
Assign 1 to reload r197 (freq=1426)
Hard reg 1 is preferable by r222 with profit 3029
Hard reg 2 is preferable by r222 with profit 1425
Assigning to 202 (cl=GENERAL_REGS, orig=138, freq=1426, tfirst=190,
tfreq=4991)...
Assign 1 to reload r202 (freq=1426)
Assigning to 195 (cl=INDEX_REGS, orig=140, freq=1426, tfirst=191,
tfreq=4278)...
Assign 5 to reload r195 (freq=1426)
Assigning to 198 (cl=INDEX_REGS, orig=140, freq=1426, tfirst=191,
tfreq=4278)...
Assign 5 to reload r198 (freq=1426)
Assigning to 203 (cl=INDEX_REGS, orig=140, freq=1426, tfirst=191,
tfreq=4278)...
Assign 5 to reload r203 (freq=1426)
Assigning to 196 (cl=GENERAL_REGS, orig=196, freq=1426, tfirst=196,
tfreq=1426)...
Trying 2: spill 225(freq=1426)
Assigning to 199 (cl=GENERAL_REGS, orig=199, freq=1426, tfirst=199,
tfreq=1426)...
Trying 2: spill 225(freq=1426)
Assigning to 204 (cl=GENERAL_REGS, orig=204, freq=1426, tfirst=204,
tfreq=1426)...
Trying 2: spill 216(freq=2139)
Assign 0 to reload r196 (freq=1426)
Assign 0 to reload r199 (freq=1426)
Assign 0 to reload r204 (freq=1426)
Reassigning non-reload pseudos
Here is the dump after lra_constraints. These are the insns related with r194,
r195, r196:
(insn 200 120 201 6 (set (reg/f:SI 194 [orig:138 D.3281 ] [138])
(reg/f:SI 138 [ D.3281 ])) 1.ii:197 89 {*movsi_internal}
(nil))
(insn 201 200 121 6 (set (reg/f:SI 195 [orig:140 D.3282 ] [140])
(reg/f:SI 140 [ D.3282 ])) 1.ii:197 89 {*movsi_internal}
(nil))
(insn 121 201 202 6 (set (reg:DI 196)
(mem:DI (plus:SI (plus:SI (reg/f:SI 99 [ D.3281 ])
(reg/f:SI 126 [ D.3282 ]))
(const_int 8 [0x8])) [10 MEM[base: _1, index: _44, offset: 8]+0
S8 A64])) 1.ii:197 88 {*movdi_internal}
(expr_list:REG_DEAD (reg:DI 131 [ D.3287 ])
(nil)))
(insn 202 121 122 6 (set (mem:DI (plus:SI (plus:SI (reg/f:SI 194 [orig:138
D.3281 ] [138])
(reg/f:SI 195 [orig:140 D.3282 ] [140]))
(const_int 8 [0x8])) [10 MEM[base: _75, index: _77, offset:
8B]+0 S8 A64])
(reg:DI 196)) 1.ii:197 88 {*movdi_internal}
(nil))
>From trace, r194 r195 are assigned hardreg before r196. Usually reload pseudos
will not conflict with each other except a special case: they are in the same
insn. r194,r195 and r196 just belong to such case. They are all in the insn
202.
In addition, r194, r195 and r196 are all reload pseudos, so once r194 and r195
are allocated, they will not be spilled for assigning hardreg for r196. In this
case, r194 and r195 get hardreg assigned before r196. So after r194 and r195
are assigned hardreg, r196 cannot find available hardreg because it has bigger
mode and require a consecutive hardreg pair. All pseudos which cannot find
hardreg after two iterations will be given ax simply, and report error. Trunk
report error but 4.8.1 doesn't report it because lra_assert is only enabled in
trunk but not in 4.8.1.
A possible fix is to give bigger mode pseudos higher priority in lra
assignment.
Index: lra-assigns.c
===================================================================
--- lra-assigns.c (revision 200944)
+++ lra-assigns.c (working copy)
@@ -194,15 +194,15 @@ reload_pseudo_compare_func (const void *
if ((diff = (ira_class_hard_regs_num[cl1]
- ira_class_hard_regs_num[cl2])) != 0)
return diff;
- if ((diff = (regno_assign_info[regno_assign_info[r2].first].freq
- - regno_assign_info[regno_assign_info[r1].first].freq)) != 0)
- return diff;
/* Allocate bigger pseudos first to avoid register file
fragmentation. */
if ((diff
= (ira_reg_class_max_nregs[cl2][lra_reg_info[r2].biggest_mode]
- ira_reg_class_max_nregs[cl1][lra_reg_info[r1].biggest_mode])) != 0)
return diff;
+ if ((diff = (regno_assign_info[regno_assign_info[r2].first].freq
+ - regno_assign_info[regno_assign_info[r1].first].freq)) != 0)
+ return diff;
/* Put pseudos from the thread nearby. */
if ((diff = regno_assign_info[r1].first - regno_assign_info[r2].first) != 0)
return diff;
The failure test is ok with this fix. bootstrap and regression test is ok.
